I'm using the glass that came with Kainoa Harbottle's Victorian Coins and Glass. As a side note regarding coins from Roy Kueppers, on the "other" forum there's been talk for years about inconsistent quality and customer service. Your mileage may vary.

It's a while since I wrote this up, but here are some thoughts on the first change...

It's nice to have the right kind of glass; you need to find one with a curved base _on the inside_. If the bottom of the glass has a severe transition between the bottom and the sides, the move becomes a lot harder. The one I have at the moment is a Nutella jar glass. If you only have a straight edged glass, the technique becomes slightly different (but I'll come to that). Also, you don't want the glass to be too much larger than your coin at the base - this also causes some issues.

Let's assume you have glass, and the coin is in the bottom. Tilt the glass forward (so the mouth is away from you) about ten degrees (that is to say, not much). We are going to do it this way to avoid flashing the bottom of the coin though the glass - a small chance, but it's there. If you look into the glass, you will see that the edge of the coin will be up against the bottom of the side. Ideally, you want the coin to begin to rise up the edge. Now, make a sharp movement _backwards_ with your hand - moving the thumb in a straight line towards your body. Resist the urge to look into the glass, as this will bring the mouth back to the vertical, and the change is harder to do. The coin will slide back to the near edge, hit it and because of the angle of the glass, it will flip over. Because the diameter of the glass is quite tight on the coin, and you don't jerk your hand back too fast, the coin will make only one flip. If it _does_ end up the same way, just flick it again.

Now, if you have a round bottomed glass, things are much easier. You can hold the glass upright, and make a short, horizontal movement forward and back. The coin will slide up the curved edge, and flip.

I'll try to get a video to explain this. I suspect that the problem is a flat bottomed glass. Check back in an hour